1. Field of the Invention
This invention relates in general to oil and gas production, and in particular to coupling segments of an electrical submersible pump.
2. Background of the Invention
Electrical submersible pumps (ESP) may be deployed within a wellbore to pump downhole fluid to the surface. Typically, an ESP includes an electrical motor, a seal section, and a pump that is driven by the motor. The pump can discharge pressurized fluid directly into the wellbore or into connected production tubing. A typical seal section includes a diaphragm that is in pressure communication with ambient pressure on one side, and on its other side in pressure communication with the motor section. A body of substantially incompressible equalizing fluid, such as a dielectric fluid, fills the diaphragm, the motor section, and the fluid paths or passageways between the diaphragm and the motor section. Maintaining the pressure within the motor section at substantially ambient pressure minimizes a pressure differential across the housing and seals of the motor section; thereby reducing the chances of a breach in the housing or seals that would allow fluid ingress.
Prior to assembling an ESP, the seal section is typically filled with an equalizing fluid and then purged of any air that may remain inside after being filled. When the ESP is vertically assembled, equalizing fluid may leak from the bottom of the seal section as it is being connected to the motor. Any voids formed in the seal section by leaked equalizing fluid, can allow compressible air to reenter the seal section, thereby partially disabling its equalizing abilities. The motor section is also typically filled with fluid prior to assembly. Generally a motor section is not prone to fluid leakage when the ESP is vertically assembled, however the motor section can leak if the ESP is horizontally assembled.